The entire population of Monowi, Nebraska, is sitting in a bar. Her name is Elsie Eiler, 72.

Monowi, founded by Czech immigrants seeking a slice of the American dream, is on its last legs. Only Eiler is left, surrounded by the ruins of homes that once boasted families, neighbours and friends.

'After me, I suppose there will be be nothing here. But I aim to be around for quite a few years yet,' she said with the stoicism that probably marked her tough ancestors. Like the Indian tribes that the settlers of the West replaced, Eiler is in turn the last of her kind, the last of Monowi.

This town is an extreme example of what has happened across America's heartland. The depopulation of the countryside over the last 50 years has been called the largest migration in American history. Nowhere is that more starkly illustrated than on the Great Plains, which includes Nebraska, Kansas and Oklahoma. They defined much of the American self-image, a land of family farms, hard work and mom's apple pie.

Monowi, and thousands of places like it, spawned the American small town values celebrated even now as the small towns themselves vanish. And you can't get more small town than Monowi.

Eiler's life as its mayor and sole resident is surreal. Once a year she raises taxes from herself to keep the four street lights on and a few other basic amenities going. She runs the town's only business, the Monowi Tavern, and lives in the only remaining habitable building. She grants her own liquor licence and elects herself mayor. Her customers come off the highway that runs through Monowi or from nearby towns. The town's welcome sign lists Monowi's population as two, a figure halved last year when Eiler's husband Rudy died.

It was not always so. Monowi - an Indian word for prairie flower - once thrived. It was founded in 1902 by European settlers lured by a promise of farms of their own. It soon had a post office, two banks, a high school, a church and rows of sturdy wooden houses. Its population probably peaked at around 150 in the Twenties.

A map of old Monowi now hangs on the age-tanned wooden wall of Eiler's tavern. It shows a grid of streets with homely names such as Louisa, Marion and Paulina. Now nearly all those streets lie beneath prairie grasses that are reclaiming them.

The pretty wooden church is boarded up. Houses stand in various states of decay. Some have collapsed completely. Others look as though their owners have just spent a year away: nothing a lick of paint and mowing the grass would not fix. In one abandoned home there is still a piano. In front of another a children's tricycle lies on what was once a front lawn.

Monowi seems hopeless but Eiler will have none of it. She's just opened a 5,000-book library just behind the tavern. This was her husband's dream project but he died before it was built. It is a hit with people from surrounding towns.

But the library's success is rare in recent Monowi history. The primary school where Eiler met her husband as a child is now a ruin. In fact Monowi's been in decline since shortly after it was founded. That is true of a lot of the Great Plains. Although settlers flocked to the land, the soil is too thin for quality farming and is soon exhausted. Changes in the rural economy, where Wal-Mart and other chain stores take almost all the business, have destroyed what remains.

That leaves behind only the old and the stubborn. Eiler happily counts herself as both. She is blunt about prospects here: 'There is just no employment for people. Farming is hard and all the small farms have had to merge into bigger ones, and the young people just want to go away to college and a city. Few of them come back.'

All over the Great Plains small towns are dying. The roll of decline is written on road signs on the road to Monowi. Obert: pop. 39, Maskell: pop. 54.

Many have tried all sorts of schemes to stay alive. Some have worked, turning them into artist colonies. The novelist Larry McMurtry turned Lucas, Texas, into a mecca for book lovers.

Others have not. Empty business parks, built with federal grants, dot the landscape. It is a reversal of the old ode: 'Build it and they shall come.'

The landscape is gradually reverting to grassland and prairie. Many farms are switching to hunting. Some have replaced cattle with buffalo, increasingly common on American dinner plates.

Twenty years ago there was a huge controversy when two academics proposed the plains be turned into a wildlife preserve called 'Buffalo Commons'. Locals and politicians, clinging on to their way of life, were outraged.

The former governor of Kansas, Mike Hayden, scoffed at the concept then. Now he thinks differently. 'I was wrong,' he said. The newest concept is a 'rewilding' of the area with animals from Africa such as elephants and camels, returning the plains to the Pleistocene ecosystem before humans arrived.

But the plains are taking matters into their own hands. Prairie wildlife is already returning as humans leave. When Eiler was growing up, deer were unheard of around Monowi. Now they are so common they are a pest.

Wild elk have returned, too. And predators not seen for a century on the plains of Nebraska are back. A handful of mountain lions roam the state and are even spotted on the outskirts of Omaha, the biggest city.

'We used never to get deer here at all. Now every day I see them come through the streets,' Eiler laughed.

A walk through Monowi is an eerie experience. The only sound is wind rustling through the grasses.

Suddenly a flock of birds shoots out of the tall grass, soaring into a blue sky. They had been nesting in thick weeds growing on what was once Main Street.